2006 DODGE RAM SRT-10 engine coolant

Theory of Operation
The engine coolant temperature sensor is a negative temperature coefficient thermistor-type sensor whose resis-
tance varies inversely with temperature. At cold temperatures the sensorresistance is high so the voltage is high.
As the coolant temperature increases the resistance decreases and the voltage becomes low.
When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition:
The Engine Coolant Temperature (ECT) Signal circuit voltage at the PCM goes below 0.8 of a volt for more
than 3 seconds.
Possible Causes
(K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND
(K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
ECT SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ECT SENSOR VOLTAGE BELOW 1.0 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the ECT voltage.
Is the voltage below 1.0 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Symptom. (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
2.ECT SENSOR
Turn the ignition off.
Disconnect the ECT harness connector.
Ignition on, engine not running.
With a scan tool, read ECT voltage.
Is the voltage above 1.0 volt?
Ye s>>
Replace the ECT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3

P0118-ENGINE COOLANT TEMP SENSOR VOLTAGE TOO HIGH
For a complete wiring diagramRefer to Section 8W.

When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition:
The Engine Coolant Temperature (ECT) sensor circuit voltage at the PCM is greater than 4.94 volts for more
than 3.0 seconds.
Possible Causes
(K2) ECT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
(K2) ECT SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
ECT SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ECT SENSOR VOLTAGE ABOVE 4.94 VOLTS
Ignition on, engine not running.
With a scan tool, read the ECT voltage.
Is the voltage above 4.94 volts?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Symptom. (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
2.ECT SENSOR
Turn the ignition off.
Disconnect the ECT harness connector.
Connect a jumper wire between the (K2) ECT Signal circuit and the
(K900) Sensor ground circuit in the ECT harness connector.
Ignition on, engine not running.
With a scan tool, read ECT voltage.
Is the voltage below 1.0 volt with the jumper wire installed?
Ye s>>
Replace the ECT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
NOTE: Remove the jumper wire before continuing.

Theory of Operation
The engine coolant temperature sensor is a negative temperature coefficient thermistor-type sensor whose resis-
tance varies inversely with temperature. At cold temperatures the sensorresistance is high so the voltage is high.
As the coolant temperature increases the resistance decreases and the voltage becomes low. The INSUFFICIENT
COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL determines if the engine coolant temperature will reach
theclosedloopfuelingcontroltemperaturelimitinaregulatedtimeafterstart.
When Monitored:
With battery voltage greater than 10.4 volts and after engine is started.
Set Condition:
The engine temperature does not go above -10°C (15°F). Failure time depends on start-up coolant tempera-
ture and ambient temperature. (i.e. 2 minutes for a start temp of -10°C (15°F) or up to 10 minutes for a vehicle
with a start-up temp of -28°C (5°F). Two Trip Fault. Three good trips to turnoff the MIL.
Possible Causes
LOW COOLANT LEVEL
THERMOSTAT
ECT SENSOR
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.CHECKING COOLANT LEVEL AND CONDITION
Ignition on, engine not running.
With a scan tool, read DTCs.
NOTE: If an Engine Coolant Temperature (ECT) DTC is set along with this code, diagnose the ECT DTC first.
NOTE: Inspect the ECT terminals and related PCM terminals. Make sure the terminals are free from corro-
sion and damage.
NOTE: The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have
a totally cold soaked engine.
NOTE: Extremely cold outside ambient temperatures may have caused this DTCtoset.
WARNING: Never open the cooling system when the engine is hot. The system isunder pressure. Extreme
burns or scalding may result. Failure to follow these instructions can result in personal injury or death.
Allow the engine to cool before opening the cooling system.
Inspect the coolant system for proper level and condition.
Is the coolant level and condition OK?
Ye s>>
Go To 2
No>>
Inspect the vehicle for a coolant leak, make the appropriate repairs, and add the correct amount of
coolant.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.THERMOSTAT OPERATION
NOTE: This test works best if performed on a cold engine (cold soak)
Ignition on, engine not running.
With a scan tool, read the Eng Coolant Tmp Deg value. If the engine was allowed to sit overnight (cold soak), the
temperature value should be a sensible value that is somewhere close to theambient temperature.
NOTE: If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is
reached.
Start the Engine.
During engine warm-up monitor the Eng Coolant Tmp Deg value. The temp deg value change should be a smooth
transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a
thermometer.
NOTE: As the engine warms up to operating temperature, the actual coolant temperature (thermometer read-
ing) and the scan tool Eng Coolant Tmp Deg values should stay relatively close to each other.
Using the appropriate service information, determine the proper openingtemperature of the thermostat.
Did the thermostat open at the proper temperature?
Ye s>>
Go To 3
No>>
Replace the thermostat.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
3.ECT SENSOR OPERATION
Ignition on, engine not running.
With a scan tool, read the Eng Coolant Tmp Deg value. If the engine was allowed to sit overnight (cold soak), the
temperature value should be a sensible value that is somewhere close to theambient temperature.
NOTE: If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is
reached.
Start the Engine.
During engine warm-up monitor the Eng Coolant Tmp Deg value. The temp deg value change should be a smooth
transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a
thermometer.
NOTE: As the engine warms up to operating temperature, the actual coolant temperature (thermometer read-
ing) and the scan tools Eng Coolant Tmp Deg value should stay relatively close to each other.
Is the thermometer reading relatively close to the scan tool ECT reading?
Ye s>>
Te s t C o m p l e t e .
No>>
Replace the Engine Coolant Temperature Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

When Monitored:
At a cold start, engine coolant below 98°F, Ambient/Battery Sensor readingwithin27°F,andEngineCoolant
Temperature above 170°F on the previous key off.
Set Condition:
The Oxygen Sensor signal voltage is below 0.156 of a volt for 28 seconds after starting engine.
Possible Causes
(K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO GROUND
(K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
O2 SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.O2 SENSOR BELOW 0.16 OF A VOLT
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Start the engine.
Allow the engine to idle for 4 to 5 minutes.
With the scan tool, read the O2 Sensor voltage.
Is the voltage below 0.16 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.O2 SENSOR OPERATION
WARNING: When the engine is operating, do not stand in a direct line with thefan. Do not put your hands
near the pulleys, belts, or fan. Do no wear loose clothing.
Disconnect the O2 Sensor harness connector.
Start the engine.
With the scan tool, monitor the O2 Sensor voltage.
IstheO2Sensorvoltageabove0.16ofavolt?
Ye s>>
Replace the O2 Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3

When Monitored:
With battery voltage greater than 10.4 volts, engine running for more than4 minutes and coolant temperature
above 180°F.
Set Condition:
The oxygen sensor voltage is above 1.5 volts.
Possible Causes
(K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K99) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT OPEN
(K41) O2 1/1 SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
(K343) ASD RELAY OUTPUT CIRCUIT OPEN
(K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO THE (K343) ASD RELAY OUTPUT CIRCUIT
O2 SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.O2 SENSOR ABOVE 1.5 VOLTS
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Start the engine.
Allow the engine to idle for 4 to 5 minutes.
With the scan tool, read the O2 Sensor voltage.
Is the voltage above 1.5 volts?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.(K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the C1 PCM harness connector.
Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the (K41) O2 Sen-
sor 1/1 Signal circuit at the 1/1 O2 Sensor harness connector.
Does the test light illuminate brightly?
Ye s>>
Repair the short to voltage in the (K41) O2 Sensor 1/1 Sig-
nal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3

When Monitored:
With ECT greater than 147°F, after reaching a vehicle speed of 10 mph, and the throttle remaining open (off
idle) for 2 minutes, bring the vehicle to a stop and allow the engine to idle with the transmission in DRIVE.
Set Condition:
The oxygen sensor signal voltage is switching from below 0.27 of a volt to above 0.62 of a volt and back fewer
times than required.
Possible Causes
EXHAUST LEAK
(K41) O2 1/1 SIGNAL CIRCUIT
(K900) SENSOR GROUND CIRCUIT
O2 SENSOR
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved sil-
icone, oil and coolant.
Ignition on, engine not running.
NOTE: After the repairs have been made, verify proper O2 Sensor operation.If all the O2 Sensor voltage
readings have not returned to normal, follow the diagnostic procedure forthe remaining O2 Sensors.
With a scan tool, read DTCs.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Symptom. (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
2.EXHAUST LEAK
Start the engine.
Inspect the exhaust system for leaks between the engine and the O2 Sensors.
Are there any exhaust leaks?
Ye s>>
Repair or replace the leaking exhaust parts as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
3.(K41) O2 1/1 SIGNAL CIRCUIT VOLTAGE DROP
Turn the ignition off.
While backprobing, measure the voltage of the (K41) O2 Sensor 1/1 Signal circuit between the 1/1 O2 Sensor har-
ness connector and PCM harness connector.
NOTE: Make sure the voltmeter leads meet the terminals in the connector andthat there is good terminal to
wire connection and are connected for positive polarity.
Start the engine.